Q. No.A coil having an area \(A_0\) is placed in a magnetic field which changes from \(B_0~\text{to}~4B_0\) in time interval \(t\). The average EMF induced in the coil will be:
1. \(\frac{3 A_{0} B_{0}}{t}\)
2. \(\frac{4 A_{0} B_{0}}{t}\)
3. \(\frac{3 B_{0}}{A_{0} t}\)
4. \(\frac{4 B_{0}}{A_{0} t}\)
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An electric potential difference will be induced between the ends of the conductor shown in the diagram when the conductor moves in the direction of:
1. \(P\)
2. \(Q\)
3. \(L\)
4. \(M\)
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The number of turns in a coil of wire of fixed radius & length is \(600\) and its self-inductance is \(108\) mH. The self-inductance of a coil of \(500\) turns will be:
1. \(74\) mH
2. \(75\) mH
3. \(76\) mH
4. \(77\) mH
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A magnetic rod is inside a coil of wire which is connected to an ammeter. If the rod is stationary, which of the following statements is true?
| 1. | The rod induces a small current. |
| 2. | The rod loses its magnetic field. |
| 3. | There is no induced current. |
| 4. | None of these. |
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| 1. | \(250\) J | 2. | \(125\) J |
| 3. | \(500\) J | 4. | \(100\) J |
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An aluminium ring \(B\) faces an electromagnet \(A\). If the current \(I\) through \(A\) can be altered, then:
| 1. | whether \(I\) increases or decreases, \(B\) will not experience any force. |
| 2. | if \(I\) decreases, \(A\) will repel \(B\). |
| 3. | if \(I\) increases, \(A\) will attract \(B\). |
| 4. | if \(I\) increases, \(A\) will repel \(B\). |
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In the figure magnetic energy stored in the coil is:
| 1. | Zero | 2. | Infinite |
| 3. | \(25\) joules | 4. | None of the above |
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Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity. If the wire AB is replaced by a semicircular wire, the magnitude of the induced current will:
| 1. | increase. |
| 2. | remain the same. |
| 3. | decrease. |
| 4. | increase or decrease depending on whether the semicircle bulges towards the resistance or away from it. |
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A wire cd of length \(l\) and mass \(m\) is sliding without friction on conducting rails \(ax\) and \(by\) as shown. The vertical rails are connected to each other with a resistance \(R\) between \(a\) and \(b\). A uniform magnetic field \(B\) is applied perpendicular to the plane \(abcd\) such that \(cd\) moves with a constant velocity of:
| 1. | \({mgR \over Bl}\) | 2. | \({mgR \over B^2l^2}\) |
| 3. | \({mgR \over B^3l^3}\) | 4. | \({mgR \over B^2l}\) |
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A coil having number of turns \(N\) and cross-sectional area \(A\) is rotated in a uniform magnetic field \(B\) with an angular velocity \(\omega\). The maximum value of the emf induced in it is:
1. \(\frac{NBA}{\omega}\)
2. \(NBAω\)
3. \(\frac{NBA}{\omega^{2}}\)
4. \(NBAω^{2}\)
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